Device for fluidized-bed jet milling

Abstract

The present invention pertains to a fluidized-bed jet mill intended to overcome the problem whereby a fluid jet introduced into the fluidized bed at high velocity takes up solid particles from the fluidized bed mainly in the area of the jet near the circumference. To have solid particles in the core area of the fluid jet as well auxiliary jets with fluidized solid particles are caused to penetrate into the fluid jet to be introduced into the fluidized bed such that the solid particles reach the core area of the fluid jet to enrich the core area with solid particles and allow an area near the circumference to receive solid particles from the fluidized bed.

What is claimed is: 
     
       1. A fluidized-bed jet mill comprising base means,   a fluidized bed disposed on said base means, said fluidized bed comprising a fluid in which there are suspended a plurality of solid particles,   a nozzle housing mounted on said base means, said nozzle housing having an exit chamber and comprising a main nozzle and a plurality of auxiliary nozzles each of which has a respective discharge end at said nozzle housing exit chamber, each auxiliary nozzle being directed for discharging a jet of gas which intersects a jet of gas from the main nozzle downstream and outside of the nozzle housing for concentrating the particles toward the center of the jet within the fluidized bed thereby enabling particles from the fluidized bed to be drawn into the gas.   
     
     
       2. A device in accordance with claim 1, wherein the auxiliary nozzles are mounted on said base means at uniformly spaced locations concentric with the main nozzle, each of said main nozzle and said auxiliary nozzle having a discharge opening in a common plane, and the direction of each of said auxiliary nozzles intersects the direction of the main nozzle at an angle in the range of 5° to 60°. 
     
     
       3. A device in accordance with claim 2, wherein the range of the angles of intersection is 25° to 45°. 
     
     
       4. A device in accordance with claim 1, wherein three of said auxiliary nozzles surround said main nozzle. 
     
     
       5. A fluidized bed jet mill comprising base means,   a fluidized bed disposed on said base means, said fluidized bed comprising a fluid in which there are suspended a plurality of solid particles, and   a plurality of respective nozzle assemblies mounted on said base means,   each respective nozzle assembly having an exit chamber and comprising   a main nozzle and   a plurality of auxiliary nozzles each of which has a respective discharge end at said nozzle housing exit chamber, each auxiliary nozzle being directed for discharging a jet of gas which intersects a jet of the discharged gas from said main nozzle downstream and outside of the nozzle housing for concentrating the particles toward the center of the jet within the fluidized bed thereby enabling particles from the fluidized bed to be drawn into the gas said nozzle assemblies being symmetrically mounted on said base.   
     
     
       6. Apparatus in accordance with claim 5 wherein each one of said respective nozzle assemblies further comprises respective control means for controlling the flow of fluid therefrom independently of the others of said respective nozzle assemblies.